HYG articles September 13

Insects on milkweed in the home landscape

Throughout the summer I receive messages from landscape professionals and gardeners asking about insects on milkweed. Often people want to learn whether the insect they’ve encountered is a pest and sometimes they ask whether that insect may be a threat to monarch caterpillars they wish to encourage in the landscape. There are a plethora of different insect species that live on milkweed ranging from tiny aphids to large butterflies and voracious mantids. Here are some of the most common insect species on milkweed throughout the summer: Herbivores Monarch butterflies and caterpillars Monarch butterflies and caterpillars (Danaus plexippus) are among the most recognizable insect species in Illinois. Monarch caterpillars feed exclusively on the foliage of milkweed plants. Adult butterflies feed on nectar from a variety of flowering plants including prairie plants, ornamental plants and plants that are often considered weeds. Monarch butterflies provide pollinating services. Pollen sticks to their bodies and is transferred from plant to plant when they visit flowers to feed. Monarchs sequester the milkweed’s natural plant defensive compounds in their bodies. These compounds make monarchs distasteful to many predators, providing a good natural defense.

Aphids

Aphids are tiny pear-shaped insects that suck the fluids from plants. Oleander aphid (Aphis nerii) is a common aphid on milkweed. These insects produce sugary droppings called honeydew which can coat leaves and support sooty mold. Dense populations can impact plant vigor but aphid populations are commonly parasitized and usually do not require control.

Aphids are sometimes tended by ants which can be problematic. Ants tending aphid colonies collect the sugary honeydew produced by the aphids and protect them from predators, preventing natural control of aphid populations. If the plant is stressed or if you are seeing dieback, it may be beneficial to treat aphids with an insecticidal soap or horticultural oil. However, these treatments may also harm young monarch caterpillars. The aphids will not harm monarchs but heavy aphid populations can stress the plants which can stress feeding caterpillars. Milkweed bugs

Milkweed bugs (Oncopeltus sp.) are very common and active this time of year. Both adults and nymphs are orange to red and black. They use a straw-like mouthpart to feed on seeds within milkweed pods but they often wander to other parts of the plant and visit nearby plants. They will not harm monarchs and, because they feed on a different part of the plant, do not directly compete with them. They should not cause significant problems for the grower unless they intend to harvest milkweed seeds. Milkweed tussock moth caterpillars

Milkweed tussock moth caterpillars (Euchaetes egle) are covered in tufts of orange, black and white hair. The tufts are in a tent-like arrangement along the length of the caterpillar’s back and stick out away from the body at the head and rear ends. It is more common to see these insects toward the end of summer when they reach this colorful life stage. This insect feeds on milkweed foliage and will not harm monarchs. Swamp milkweed leaf beetles

Swamp milkweed leaf beetle (Labidomera clivicollis) adults have orange wing covers with variable black patches. They are similar to lady beetles in body shape but they are larger. Larvae have robust fleshy abdomens that are gray to orange with a line of small black spots along each side. Swamp milkweed leaf beetles feed on the foliage of the milkweed plants as larvae and adults. They will not harm monarchs.

Milkweed longhorn beetles Milkweed longhorn beetles (Tetraopes sp.) have black

antennae, red bodies and red wing covers with black spots. One of the major identification characteristics for longhorned beetles is that their antennae are longer than the length of their bodies. The adults feed on milkweed foliage and buds, lay eggs on milkweed stems and the larvae feed within milkweed roots. Milkweed longhorn beetle adults have bright coloration and are usually slow moving so they can be easily spotted, identified and observed. Milkweed longhorn beetles will not harm monarchs. Insectivores Lady beetles Lady beetles (family Coccinellidae) are another easily recognized insect, they have red wing covers with black spots and black and white hear and pronotum. Their larvae have long bodies with spike-like projections. They have three pairs of jointed legs near their head and are black and orange. Both the larvae and adults are insect predators, commonly found on milkweed. Lady beetles feed on tiny insects that live on milkweed, especially aphids. They do not harm monarchs. Soldier beetles

Adult soldier beetles (family Cantheridae) are omnivores, feeding on pollen and nectar from flowers and small insects like aphids. Soldier beetle larvae also feed on small insects in the soil. Adult beetles are orange with a black spot on each wing cover. This species is considered beneficial because they pollinate flowers and feed on small insects so control is not recommended. Ambush Bugs

Ambush bugs (subfamily Phymatinae) are named for their predatory behavior. They sit still on milkweed and other plants, often on the flower, and wait for small prey insects to approach. When a prey insect is within reach, they grasp the insect with their raptorial forearms and begin to feed. They can feed on a variety of insect which can make them beneficial predators.

These insects are well camouflaged, with brown and yellow to green bodies. They can be distinguished from similarly shaped insects, like stink bugs or assassin bugs, by the shape of their forelegs which look similar to those of a praying mantis or Tyrannosaurus rex. While adult monarchs are too large and distasteful for this insect to capture, ambush bugs have the potential to consume young caterpillars.

Spined soldier bugs Spined soldier bugs (Podisus maculiventris) are predatory stink

bugs. Adults are brown with a spine on each side of their pronotum (shoulder area). The young nymphs are often orange and black or green and black. These predators actively hunt and feed on prey insects. Their diet can include a range of insects which makes them beneficial predators in the landscape. However, their diet could include monarch caterpillars larger than themselves. Praying mantids

Praying mantids (order Mantodea) are easily recognized by their long bodies and raptorial forelegs. There are two species of mantids in Illinois, the native Carolina mantis (Stagmomantis carolina) and the introduced Chinese mantis (Tenodera sinensis). The Chinese mantis is much larger than the Carolina mantis and has a yellow spot between its forelegs. Adult manitids are large enough to attack and consume an adult monarch butterflies but are unlikely to consume more than one because they learn that the monarchs are distasteful. They are also capable of consuming monarch caterpillars. They are unlikely to consume the caterpillars repeatedly because they are also distasteful. However, in laboratory studies some Chinese mantids learned to avoid milkweed material inside caterpillars by not consuming the caterpillar’s gut while feeding. If you or your clients are concerned about mantids feeding on monarchs, I recommend relocating mantids to an area without milkweed. Mantids can be beneficial predators in other parts of the garden or landscape. Pesticide applications on milkweed could be harmful to any insects that enter the area, including monarchs. Image Credits: Monarch (Danaus plexippus) adult on purple cone flower, Sarah Hughson, University of Illinois at

Urbana-Champaign Oleander aphid (Aphis nerii) and monarch caterpillar (Danaus plexippus) on milkweed, Sarah Hughson,

University of Illinois at Urbana-Champaign Milkweed bug on milkweed, Sarah Hughson, University of Illinois at Urbana-Champaign Milkweed tussock moth (Euchaetes egle), Ansel Oommen, Bugwood.org Swamp milkweed leaf beetle, Sarah Hughson, University of Illinois at Urbana-Champaign

Milkweed longhorn beetle on milkweed, Sarah Hughson, University of Illinois at Urbana-Champaign Convergent lady beetle (Hippodima convergens), Jerrod Hein, Kansas State University, Bugwood.org Goldenrod soldier beetle (Chauliognathus pensylvanicus), David Cappaert, Bugwood.org Ambush bugs (Phymata sp.), David Cappaert, Bugwood.org Spined soldier bug (Podisus maculiventris), John Ruberson, Kansas State University, Bugwood.org Carolina mantis (Stagmomantis carolina), Sarah Hughson, University of Illinois at Urbana-Champaign

Ragweeds in Lawns and Landscapes If you suffer from pollen allergies this time of year, you are likely familiar with the ragweeds. Both common ragweed (Ambrosia artemisiifolia) and giant ragweed (A. trifida) are typically found in waste areas, fields, and rural roadsides. This year, however, I have seen common ragweed on more than one occasion happily growing in mowed turfgrass in an urban setting. I could maybe understand if it were growing in a rural lawn. Still, this is not a common lawn weed. To make matters worse, the ragweed was IN BLOOM. Take that, allergy sufferers! It’s growing close to the ground where you aren’t even looking for it.

Common ragweed in bloom in a lawn.

While both common and giant ragweed are related and similar in some aspects, there are noticeable differences. Both grow as erect, summer annuals with primarily fibrous roots. While common ragweed typically grows 1 to 4 feet tall, giant ragweed grows 4 to 8 feet tall, but in fertile, moist soils, it can reach 12-18 feet. While the leaves of common ragweed are mostly alternate, nearly smooth, and deeply cut into a number of lobes (fernlike), in contrast the leaves of giant ragweed are opposite, rough, hairy, and large with three to five lobes. Both plants have small, green, inconspicuous flowers that produce an abundance of pollen that is hazardous to hay fever sufferers. This quality is the reason that both ragweeds have earned a spot on the Illinois Noxious Weed Law species list.

Common ragweed in a landscape bed. Certain weeds have been legally declared noxious by the Illinois legislature. Their control is required by law. The Illinois Noxious Weed Law states that “every person shall control the spread of” and “eradicate all noxious weeds on lands owned or controlled by him in the state of Illinois.” The law further states that, “whenever the owner or person in control of the land on which noxious weeds are present has neglected or failed to control or eradicate them . . . the control authority having jurisdiction shall have proper control and eradication methods used on such land, and shall advise the owner, person in control, and record holder of any encumbrance of the cost incurred in connection with such operation. The cost of any such control or eradication shall be at the expense of the owner.” In addition, the person shall be subject to a fine of not more than 100 dollars for the first offense and not more than 200 dollars for each subsequent offense. Bear in mind however, that enforcement authority lies at the county level and funding and personnel for these efforts aren’t always readily available. Some counties strictly

enforce the Noxious Weed Law and others do not. My intent of this article is not to scare readers, but merely to make them aware.

Giant ragweed in a grassy waste area. For lawns, ragweeds can be prevented with proper practices that would lead to a dense, actively growing turfgrass. Mow high to shade out weeds. Fertilize and water at appropriate times. Select adapted turfgrass that are well suited for your growing conditions. For landscape beds, mulch can be used to prevent seeds from germinating. Certainly, preventing existing weeds from producing seeds would be best. Preemergent herbicides such as isoxaben can be used in the spring to prevent ragweed. Plants can be removed by hand or with a postemergent broadleaf herbicide such as 2,4-D or a 3-way product in lawns. For best success, apply to young plants. For spot applications, glyphosate could be used, however, it is suspected there are glyphosate resistant populations in the state so adequate control may not be achieved with this active ingredient. Read and follow all product labels carefully.

Michelle Wiesbrook

Seedy Facts One of the best management practice in the home landscape is not allowing annual weeds to flower and set seed. The story goes a bit deeper than that in terms of why that is so important. One gardening phrase that has been around for decades, if not generations is “One Year’s Seeding – Seven Years Weeding” and that is a very conservative estimate. According to the Weed Science Society of America and other Weed Science Societies, there will be plenty of weed seed viable in the soil for decades! Some are readily seen as they spread like dandelion seeds blowing across the yard like mini tumbleweed or floating in the wind. Dr. Robert Norris, Ph.D. and fellow of the Weed Science Society of America notes that besides dandelion, sowthistle and groundsel are also windborne. Others do not care to spread themselves around so obviously. Chickweed a winter annual happily produces seed for weeks and just drops them down to the soil below. Very few annual weed seeds move in other ways. Given the opportunity, a gardener can reduce that seed bank waiting to sprout when the conditions are right. Over 90% of our weed seed typically germinates in the spring, focusing on seed germination prevention and dealing with the weeds while they are just emerging and easily managed. Gardeners can create a stale seedbed by very lightly and shallowly working the very surface of the soil repeatedly, causing weed seed to germinate until the seed bank in that thin layer of soil is exhausted. Others will use a quality mulch/compost to keep those seeds in the dark to prevent germination. If there is time and space, putting soil solarization in your rotation for vegetables for example, becomes a real option. Dr. Mark Renz working from literature from the California Weed Science Society’s “Principles of Weed Control, third edition,” compiled information of a number of weeds, providing the number of seeds produced by a single plant and long we can expect them to be viable in the soil. Here are a few common weed plants we find every year in our beds: Common purslane giving us 1,800,000 seeds annually with the good news they may only last about 5 years in the soil. Compare that to Eastern Black Nightshade only giving up 825,000 seeds, BUT lasting 40 or more years. I pick the purslane! Chickweed mentioned earlier can produce 25,000 seeds that immediately fall to the soil. The University of Massachusetts lists our troublesome crabgrass as producing about 150,000 seeds every year. Crabgrass is not limited to growing in the lawn either. Wonder why we never seem to get rid of purslane, if one plant can give us 1,800,00 seeds, how many do we pull or hoe out in one year avoiding seed set?

In the end, gardeners should do whatever they can to limit seed production and over the seasons that weed seed bank will go down and won’t you be surprised one spring when your plants win over the weeds. (Richard Hentschel, Extension Educator)

Hackberry Island Chlorosis Island Chlorosis is a common disease of hackberry. While I am never surprised to see this disease, its occurrence seems to be a bit more noticeable this year. Symptoms appear as a rather interesting blocky mosaic pattern of yellow, cream, and light green spots intermixed with healthy green tissues. The lesions are delineated by veins, giving them an angular appearance.

Hackberry island chlorosis was initially suspected to be the result of a phytoplasma, virus, or possibly a physiological abnormality. My most recent search of published journals turned up little information on this disease. The strongest result was an abstract for a presentation by Benham Lockhart, a professor of plant pathology at University of Minnesota. That abstract linked disease symptoms to a previously undescribed virus. Unfortunately, no additional publications were available on this virus. While it may seem surprising that so little research has been done on such a noticeable disease, it’s likely due to the fact that it doesn’t seem to harm the tree’s health. No controls chemical controls are available, or warranted. Instead, focus efforts on practices that encourage the tree’s vitality, such as watering during drought, fertilizing as needed and proper pruning. (Travis Cleveland)

Accidental Pesticide Poisonings- Don’t let Look-alikes Fool You Pesticides can be beneficial in many ways. However, they can also pose a human health hazard when not properly handled or stored. An average of 130,136 calls to poison control centers was reported from 2006 to 2010, with an average of 20,116 cases (17.8%) treated in health care facilities annually. A report written on Human Exposures to Pesticides in the U.S. found that an average of 23 deaths occurs each year with pesticides as the underlying cause of death, mostly due to suicidal ingestions. While ingestion is not a common route of pesticide exposure, it can result in the most severe poisoning. Additionally, children are at a higher risk because they often ingest a higher dose of pesticide (amount of pesticide per pound of body weight.) In 2008, pesticides were the ninth most common substance reported to poison control centers, and approximately 45% of all reports of pesticide poisoning were for children. There are numerous reports of people accidentally drinking pesticides that were improperly stored in unlabeled bottles or beverage containers. We often think of poisonings like this as something that only happens with children, but it is also easy for adults to mistake one product for another. Pesticides can look the same as food and beverages, have similar packaging, and be accidentally ingested when not properly stored. The Pesticide Safety Program (PSEP) recently had a table display of many conventional pesticides and their look-a-likes at the University of Illinois’ Agronomy Day. It was an eye-opener for many to see the pesticide and the food product side by side. Many of the products had no visual difference at all between the two. The display brought up many stories from visitors about incidences that had occurred within their family or a friend from an accidental poisoning where pesticides had not been stored in the original container, or the label had fallen off.

This herbicide was indistinguishable from grape juice when removed from its labeled container.

The first story was how two jugs sat side by side in the garage, neither with a label. A family member was asked to get oil for the fryer. Unintentionally reached for the herbicide and ended up frying all the fish for supper that evening in an herbicide. The second story was how the pesticide was in a food container in the garage. The family was out in the garage working on a car, and the child wanted a drink. The child grabbed the bottle and drank. When the family realized what had occurred, ask the child why he didn’t spit it out as it didn’t taste good, he answered, “he didn’t want to be rude.” These stories were not fatal ones, but all left a lasting impression on the need to keep pesticides in original containers and with label secured. PSEP created a fact sheet of 10 things that people can do in order to prevent these types of incidents from occurring. Sharing this information with family members, coworkers, and friends can help to stop events like this from happening. What can you do? Here are some simple prevention tips: 1. Store pesticides in their original containers, with the label identifying the product. Never store

pesticides in food/beverage containers. 2. Store pesticides in a location separate from food & feed. 3. Secure pesticides in a locked location. 4. Keep pesticides out of the reach and sight of children. Children’s bodies are small, so even small

amounts of poisonous chemicals can cause significant problems. 5. Have adequate light in storage areas so that the labels can be seen or read easily. 6. Read labels to find out if and how pesticides could be harmful. 7. Dispose of unwanted pesticides and pesticide containers properly. 8. Teach children about pesticides and pesticide look-alikes. 9. Apply “Mr. Yuk” stickers to poisonous products. www.upmc.com/Services/poison-center/store 10. Poison Control Centers are not just for emergencies. They are open 24 hrs a day, 7 days a week as a

resource for help and information 1-800-222-1222. (Maria Turner) https://www.ccohs.ca/oshanswers/chemicals/pesticides/health_effects.html https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5813803/